Conventional IC device tests are generally carried out by picking up the IC molded dies with a using vacuum picker arms. DUTs are then placed on a test site with pivoted gold test fingers to test on the IC dies.
U.S. Pat. No. 5,894,217 shows a test handler having a turn table in which IC devices where a suction force is used to pick and place the said IC devices. U.S. Pat. No. 6,031,384 describes an IC testing method and apparatus where IC devices are carried and tested using a loader arm, an unloader arm and a contact arm without creating a vacuum for testing the said DUTs.
In testing IC devices, an automatic test handler is frequently used in combination with an IC tester to automatically move IC devices (DUT) to a test position at the test head of the IC tester. There are generally two types of test handlers. A vertical transfer type handler transfer the DUTs in a vertical direction by use of gravity. A horizontal transfer type handler places DUTs on a tray or carrier module for transfer in a horizontal direction to the test position. The test apparatus/test handler of the present invention is directed to a vertical transfer type handler.
In a typical horizontal type testing apparatus test handler, IC devices are aligned on a tray in a loading area and picked up, one by one, transferred to a test head of an IC tester and placed on a test socket of the test head by a pick and place mechanism or a robot hand of the test handler. The tested IC devices are taken from the test head and transferred to an unloading area and placed on a tray based on the test results.
In this type of test handler, the overall path of movement of the DUTs is lengthy and complicated. A relatively long time is required for positioning the DUT with the test socket, testing the DUT, and returning the tested IC device to the unloading area.
Index time, as defined in semiconductor industry, is the overall time required for handling IC device other than the time required for device testing. Since the index time is not the actual time for testing of the DUT, it is generally considered that the shorter the index time, the higher the test efficiency of the testing apparatus. A conventional test handler requires a relatively long index time because of the length of device transfer paths and complicated movements of the test handler.
A modem IC device has a large number of pins with a small pitch. Each pin is very small in size and is mechanically weak. Thus, precise positioning is required to accurately place the IC device in a test position to match with the test socket with a large number of corresponding contact pins during testing. As fine positioning of the IC devices needs complicated adjustments and synchronization of various components, errors tend to arise in placing or extracting the IC devices with respect to the test socket. This may deform the pins of the DUTs and thereby make the test unreliable.
An example of a conventional type test handler is shown in FIG. 2.
FIG. 2 is a schematic diagram showing a plan view of a test handler (100). A tray (20) having the IC devices to be tested is transferred from the loading area to a transfer station (21) (dotted line) where each of the IC devices is picked up by a suction end (10) of a pick and place mechanism and transferred to a test socket (31) positioned at the test head of an IC tester.
The suction end (10) is movable along the arm (50) in a back and forth direction (Y). The contact arm (50) can move in a right and left direction (X) along rails (40). Thus, the suction end (10) can freely take a position by the movement in the X and Y directions on a surface of the test handler (100).
By placing the IC device on the test socket (31), an IC tester (not shown) supplies test signals to the IC device on the test socket (31) and the resulted output signals from the IC device are evaluated by the IC tester. The suction end (10) picks up the DUTs that have been tested and transferred to a tray on a receiving station (22) (dotted line). It then places the IC devices depending on the test results. The IC devices on the tray are transferred to an unloading area (23) where the IC devices are unloaded with the trays for the next process, such as a molding, burning, packing and shipping for customers.
FIG. 1 is a side view showing an example of a suction end used in the pick and place mechanism of FIG. 2. In this example, the suction end (10) is provided with an air pipe (not shown) connected to an air cylinder to provide a suction air force. When a suction is applied, the suction end (10) attracts the IC device below and picks up the IC device by the suction air force. The suction end (10) is movable in the X and Y directions on the testing apparatus. The suction end (10) transfers each IC device from the transfer area (21) to the test socket (31) and from the test socket (31) to the receiving station (22).
During the process involved in the conventional testing apparatus/handler, the operation of placing the IC device on the test socket (31) sometimes fail because of an inaccurate positioning of the IC device with respect to the test socket. Such inaccurate positioning may occur when the suction end (10) picks up the IC device while moving in the X and Y directions at a relatively high speed. Suction end (10) may therefore not accurately place the DUT in the desired position when placing the IC device. The suction end (10) also may fail to accurately position the DUT due to the poor surface condition of an IC device, mechanical vibrations, or other factors.
Therefore, in the conventional testing apparatus/handler as exemplified in FIGS. 1 and 2, a relatively large index time is needed for supplying IC devices to the IC socket. As a result the test efficiency is limited by the index time. In addition, positioning errors sometimes occur because of the inaccuracy of the pick and place mechanism of the testing apparatus/handler.
Moreover, all dies must be molded during testing on apparatus/handler in order to conduct tests. This wastes the die casting materials. Physical contact with pivoted gold test fingers or test sockets may also cause severe damage to the IC.